1. Field of the Invention
This invention relates to intra-oral viewing systems. In particular, this invention relates to intra-oral camera systems for viewing teeth, gums and the like inside a patient's mouth in ambient light. Furthermore, this invention relates to intra-oral viewing systems that have an adjustable focal length from 5 mm to infinity.
2. Description of the Prior Art
In recent years, dentists and oral physicians have begun to include intra-oral cameras in their practice. Intra-oral cameras enable a dentist to view portions of a patient's mouth on a video monitor. The intra-oral camera is placed within a patient's mouth and aimed at an object of interest. An image of the object is transmitted from the intra-oral camera to a video monitor. The image, such as a tooth, can be carefully viewed on the monitor by both the dentist and the patient. Such a system allows a dentist or physician to better provide an accurate prognosis and also allows a patient to be better informed of a medical condition by the dentist or physician.
U.S. Pat. No. 5,115,307, issued May 19, 1992, to Cooper et al., discloses an electronic video dental camera which requires lens prescription attachments for changing the magnification, field of view and focal length of the video dental camera. Although it is advantageous to make optical prescription changes, Cooper '307 requires that the video camera be removed from the patient's mouth while a different lens prescriptions are snapped onto the tip of the camera. Thus, instantaneous focus and field of view changes are not possible.
U.S. Pat. No. 4,858,001, issued Aug. 15, 1989, to Milbank et al. , discloses an endoscope which is fully immersible in liquid media. The endoscope is capable of presenting an image for real-time viewing or recording a playback at a later time. This disclosed invention is not specifically designed for intra-oral examination and is not capable of changing the focal length, field of view and magnitude of zoom. Milbank '001 is based on a fiber optic system which limits the focal abilities of the camera.
U.S. Pat. No. 5,124,797, issued Jun. 23, 1992, to Williams et al., discloses a micro video imaging camera. The micro video camera has an internal lens system, but the focal length, field of view and/or zoom of the lens can not be changed after the apparatus is constructed as disclosed.
U.S. Pat. No. 5,051,823, issued Sep. 24, 1991, to Cooper et al., discloses a dental instrument having both a laser and an electronic video dental camera. The camera uses a charged coupled device (CCD) and is located at the distal end of the dental instrument. There is a slide switch on the outside of the camera casing for manipulating the angular position of a flexible light probe. The camera's focal length is not adjustable due to the use of a fixed position focal lens. Furthermore, the distal end of the Cooper '823 apparatus is large, bulky and possibly difficult to maneuver easily inside a patient's mouth.
U.S. Pat. No. 5,016,098, issued May 14, 1991, to Cooper et al., discloses an electronic video dental camera for viewing the inside of a patient's mouth. The apparatus' distal end has interchangeable attachments which change the optical characteristics of the camera. For example, the interchangeable attachments include a telephoto lens, wide angle lens, relay lens, and various translumination devices. The attachments can only be changed when the device is not in use and therefore requires the doctor to remove the camera from the patient's mouth, change the lens, then replace the camera in the patient's mouth and relocate the object of interest.
All the above described oral cameras are disadvantageous for a variety of reasons. First, none of the disclosed apparatus allow a dentist or physician to vary the focal length of the camera without physically changing a lens. Furthermore, the related art generally requires an additional light source, other than ambient light in order to produce a clear picture.